Fluid pressure operated devices for radially expanding portions of or testing tubing are known, such devices being disclosed in U.S. Pat. Nos. 1,448,457; 2,479,702; 2,938,562; and 3,200,627. Structures of these patents include fluid conveying mandrels receivable within the tubes, means for expanding the mandrels to hold the tubing, and die elements against which portions of the tubes are flared or otherwise formed by fluid pressure. These expanding devices are customarily used to provide shaped bulges in tubing for coupling purposes and the like. In addition, they are used to expand tubing to fit fins and other apparatus connected to the outer surface of the tubing.
Several hydraulic chucks have been developed which are suitable for tightly gripping one end of the elongated tube while simultaneously delivering a tube expanding or testing fluid. Among these are U.S. Pat. Nos. 3,505,846; 3,813,751; 3,962,769; and 4,189,162.
One of the problems which has plagued users of hydraulic chucks is the inability of such previously described chucks to fasten operably to the ends of the tubes without damaging the tube, particularly where the tube end is threaded for connection to other equipment. Threaded tubes are particularly susceptable to damage, which then involves costly repair.
One method which obviates damage to the threads is to design the chuck so that it can be threaded into or onto the tube. Because several revolutions of the chuck are required, it is often times necessary to disconnect the chuck from pneumatic or hydraulic sources. More important, seals must be provided which can withstand the high hydraulic pressure which is applied to the tube through the chuck.
Hydraulic chucks should be designed to be used with a vast multitude of tubes, and should not require repair or servicing for long periods of time. Yet often times the seals which may be provided often times are damaged by contact with the tube or tube threads, or the seals wear out from use. It is expected that seals will, in time, need replacement. Replacement should not be a major engineering effort, nor should it be necessary to worry about seal alignment or wear during installation.
Accordingly, it would be of great advantage if a hydraulic chuck could be provided which would easily connect to threaded tubes, and particularly male threaded tubes, and which would permit quick and damage free connection to the tube. The device must be capable of mounting or connecting on the tube without constant disconnection of the hydraulic or pneumatic lines. Damage to the tube, and to the chuck and chuck seals should be minimal at most.